I didn't see this as an explicit requirement, but less clueful backbones (Genuity, PSI, and now C&W) do tend to drop peering sessions with other backbones that push far more traffic than they pull.
Read section IV of their policy again: IV. Traffic Requirements A. Each peering connection speed shall be at least 155 Mbps. B. The traffic volume at each peering connection shall be at least 45 Mbps. C. The aggregated traffic ratio shall not exceed a ratio of 2 : 1 D. Traffic volumes shall be measured in either direction, inbound or outbound, whichever is higher, on a weekly aggregated average basis over all the points where the parties exchange traffic Point C says 2:1, but D says they don't care in which direction its in, it just has to be balanced. -Scott